Heterogeneous methanol reforming is industrial practice carried out by reacting methanol in the presence of copper-based catalysts according to the following equations:CH3OH+H2O=3H2+CO2  (1)CH3OH=2H2+CO  (2)
The methanol reforming catalyst also catalyses the Water Gas Shift (WGS) reaction,CO+H2O═CO2+H2  (3)and the Reverse Water Gas Shift (RWGS) reaction,CO2+H2═CO+H2O  (4)
In large-scale hydrogen plants, the main route for the preparation of hydrogen rich gas is steam reforming of hydrocarbons. Typically, the hydrocarbon feed is subjected to a purification step where traces of sulphur, chloride etc. is removed. From the purification step the feed is heated and steam-reformed in fired tubular reactors. The usual temperature range for steam reforming is 700-1100° C. The reactor is heated with fired heaters. Alternatively, an autothermal reforming can be used.
It is further known to steam reform methanol to synthesis gas involving the above mentioned reaction (1) and (4). Both reactions are moderately endothermic and methanol reforming is favoured by low pressure. The conversion is limited by the thermodynamic equilibrium constant. Typically a temperature of 250-300° C. is used at moderate pressures. The reaction is usually carried out in the gas form, wherein gaseous phase of methanol and steam is contacted with a methanol reforming catalyst.
Several catalysts are known to be active in steam reforming of methanol to hydrogen in the gas phase. Those catalyst compositions include copper, zinc, palladium and/or platinum (U.S. Pat. No. 6,583,084), aluminum, copper and at least one metal atom selected from iron, ruthenium and osmium (U.S. Pat. No. 6,589,909) and manganese, copper and chromium (U.S. Pat. No. 4,407,238). The most typical catalysts being employed in the industry are the copper, zinc and aluminum and/or chromium catalysts.
U.S. Pat. No. 6,699,457 discloses a process for the production of hydrogen from oxygenated hydrocarbons in the vapour phase or condensed liquid phase in the presence of a metal-containing catalyst. The catalysts contain a Group VIII transition metal or alloys of the metals. Preferred catalysts for this process are nickel, palladium, platinum, ruthenium and rhodium iridium. The oxygenated hydrocarbons for use in the process have from 2 to 12 carbon atoms. When the reforming reaction is carried out in the liquid phase, glucose, sorbitol and sucrose are a preferred feed stock for the reaction.
It has now been found that methanol reformable in the liquid phase by contact with a copper-zinc-aluminum oxide and/or chromium oxide catalyst being suspended in a suspension liquid comprising methanol and water, whereby hydrogen or synthesis gas is formed at the surface of the catalyst and leaves the reactor in the gas phase.